1. Field of the Invention
This invention relates generally to signal adaptor boards used for adapting signals between a printed circuit board and an integrated circuit having signal requirements not provided by the printed circuit board. More particularly, the invention relates to an adaptor board for converting a power supply voltage from a printed circuit board to a second power supply voltage required by an integrated circuit.
2. Discussion of the Related Art
Printed circuit boards (PCBs) include one or more rigid or flexible layers of a dielectric material having conductors fabricated upon or within the material. A PCB is designed to receive separately manufactured electrical components and to interconnect those components to create a more complex circuit.
There are many instances in which an electrical component on a PCB is replaced with a component having a different pin configuration or different signal requirements. For example, a computer user may upgrade a computer to include a more powerful microprocessor that requires a lower power-supply voltage than did the original microprocessor. Unfortunately, such changes often necessitate replacement of an otherwise good PCB.
Many manufacturers use an "adaptor card" to avoid the expense of replacing a PCB when upgrading a component. An adaptor card is designed to be placed between the PCB and the new component. Any required changes to the interconnect architecture are accomplished by the adaptor card instead of on the PCB, obviating the need to alter or replace the PCB. An adaptor card can be surface mounted to a larger PCB using wave solder techniques. Alternatively, an adaptor card can be "plugged" into sockets arranged upon the PCB, and the electrical component can be surface mounted or plugged into the adaptor card. The adaptor card is configured to compensate for any modifications to the component pin-out, modifications to signals sent to and from the component, or modifications to the operating characteristics of the component. Thus, using an adaptor card obviates the need to rework the larger PCB when upgrading a component.
FIGS. 1A and 1B illustrate a prior-art interconnect system 10 including an adaptor card 16 electrically and mechanically connected between an electrical component 14 and a PCB 12. A plurality of board sockets 18 are arranged within one surface of PCB 12 and are used to mechanically receive plugs 20 (also at times called "pins") aligned therewith. Mating plugs 20 and sockets 18 electrically connects printed conductors 22 within PCB 12 and printed conductors 24 within adaptor card 16. Any modifications to the interconnect layout between PCB 12 and component 14 can be effectuated entirely within printed conductors 24 instead of printed conductors 22. Moreover, changes in the signal timing or signal level within one or more interconnect paths can be made by component 26 retrofitted on card 16 instead of on PCB 12. Component 26 is any component that adapts or modifies signals sent across conductors 24 or conductors 22.
FIGS. 1A and 1B show a signal V routed in a printed wire 28 within PCB 12. Signal V is therefore shown as a signal transferred within conductors embedded in PCB 12 and is electrically connected to one or more PCB sockets 18. PCB socket 18 is adapted to receive pass-through plug 29 (FIG. 1B) to transfer signal V from PCB 12 to adapter card 16. Adapter card 16 can then convert signal V and present the converted signal back to a non-pass-through socket 30. Nonpass-through socket 30 allows connection of the converted signal V to a corresponding pin location 32 without transferring the converted signal back to a corresponding socket in PCB 12. The embodiment of FIGS. 1A and 1B provides interconnect routing of signal V to and from signal converter 26 and also provides pass-through of non-converted signals.
Pass-through and non pass-through of select signals are achieved using appropriately placed pass-through vias 34 and non pass-through vias 36. Each pass-through via and each non pass-through via extends entirely through adapter card 16 in a straight line perpendicular to the opposing surfaces of card 16. The non pass-through plug 36 prevents electrical conduction to an underlying socket contained within a PCB 12. Pass-through plug 52, however, does maintain electrical connection to underlying PCB 12 and can be used to receive and pass-through signals to a corresponding pin of adaptor card 16.
An unfortunate aspect of conventional adaptor card 16 is the lateral displacement of component 26. This displacement adds length to conductors 24 and necessitates the extension of adaptor board 16 well beyond the lateral boundaries of component 14. This lateral extension is problematic in many applications because the additional length of adaptor card 16 interferes with components or structures adjacent to component 14. Furthermore, the added conductor length required to displace component 26 increases the parasitic resistance, capacitance, and inductance of the elongated signal paths. These changes can adversely affect the speed performance of component 14.